Tire pressure and proper upkeep have a direct impact on the performance and longevity of tires themselves, and further-reaching effects in terms of fuel savings and fleet operating costs. With so much riding on effective pressure measurement, fleets and drivers are looking to tire pressure and temperature monitoring systems in growing numbers. As part of the Bendix Tech Tips series, Bendix Commercial Vehicle Systems LLC offers guidance on typical tire pressure monitoring system alerts, along with installation and maintenance tips for systems with sensors mounted inside the tire.

“Ninety percent of all tire failures are caused by under-inflation, and almost half of all emergency service calls are tire-related,” said Jon Intagliata, product manager for Tire Pressure Monitoring Systems (TPMS) at Bendix. “A tire pressure monitoring system can provide the crucial information that enables fleets and drivers to address potential failures before they occur, improving tire life, fuel economy, and safety.”

Tire pressure monitoring systems vary depending on the manufacturer, but generally operate on the same core principle: Sensors mounted in each wheel of a tractor and/or trailer constantly measure a tire’s pressure and, if mounted inside the tire, its temperature. This information is transmitted wirelessly and displayed by either an in-cab display or a technician’s hand-held device during maintenance checks.

A typical TPMS in-cab display usually provides alerts that notify the driver of potential problems depending on the severity of the situation.

  • Pressure deviation alert: If a tire deviates a designated percentage from its proper inflation pressure, the system activates a warning light and, possibly, an audible alarm.
  • Critical low-pressure alert: This alert activates when a tire’s pressure falls significantly below its cold inflation pressure value (usually set at 20 percent). This visual and audible warning represents the need to take immediate action.
  • High-temperature alert: In systems equipped with temperature-measuring intire sensors, this alert signals a high tire temperature that exceeds a predefined threshold – typically 185 degrees Fahrenheit. High tire temperatures are usually caused by underinflation, which means that low pressure alerts will typically occur well in advance of a high-temperature alert. Triggered on its own, this alert can indicate an alternative problem, such as a dragging brake or wheel bearing failure.
  • Low sensor battery alert: When the battery in a sensor nears the end of its life, it should be replaced as soon as possible to ensure continued accurate measurement.

These alerts will vary depending on the TPMS, as well as a system’s pressure and temperature thresholds. The more advanced TPMS systems offer customization of the alerts based on a fleet’s or driver’s needs and operating conditions.

  • Always complete the installation with the rim standing up.
  • Once the mounting strap has been measured to the proper length to hold the sensor in place around the wheel, the excess strap length should be cut off prior to final installation. Never bend the strap to break it off after you have installed the sensor.
  • Sensors should be placed at or near the valve stem to facilitate locating the sensor after the tire has been mounted.
  • When mounting sensors on dual wheels, make sure the valve stem positions and thus, the sensors – are offset 180 degrees from each other, to ease in locating the sensor when initiating with a hand tool.

Bendix provides commercial fleets, technicians, and drivers with the tools they need to ensure safe operation through assessment, maintenance, and repair. The Bendix On-Line Brake School at www.brake-school.com provides 24/7/365 access to the company’s knowledge database and technical resources on all aspects of electronics and air brake maintenance and product education. The online school delivers a series of videos on the SmarTire® TPMS system ranging from installation to troubleshooting.

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